Subaru EJ204 Specifications
| Engine Model: Subaru EJ204 |
| Engine Type: 4-cycle 4-cylinder DOHC 16-valve turbocharged liquid-cooled gasoline |
| Total Displacement: 121.7 cu.in (1.99 L) |
| Rated Engine Power: 147-160 Hp (108-118 kW) at 6200 rpm |
| Fuel System Type: Sequential multi-point electronic fuel injection (MPFI) |
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The Subaru EJ204 is a 2.0-liter,
horizontally-opposed (flat-four), dual overhead camshaft (DOHC),
16-valve, naturally aspirated gasoline engine. It is a member of the
Phase 2 generation of the ubiquitous EJ series, produced from the late
1990s through the mid-2000s. This engine was engineered primarily for
the Japanese Domestic Market (JDM) and certain European/Asian markets,
serving as a modern, refined, and efficient naturally aspirated
powerplant for Subaru's Legacy, Impreza, and Forester models.
It incorporates key Phase 2 updates including a coil-on-plug ignition
system, a redesigned intake manifold, and Subaru's Active Valve Control
System (AVCS) variable valve timing on the intake camshafts. The EJ204
is renowned for its smooth, linear power delivery, excellent
reliability, and respectable fuel economy for a symmetrical
all-wheel-drive vehicle.
While lacking the explosive power of its turbocharged EJ20 siblings, it
offers a balanced and refined driving experience with strong mid-range
torque suitable for daily driving. It is considered one of the most
durable and trouble-free iterations of the EJ20 family when properly
maintained, prized for its mechanical simplicity and longevity.
Engine Family / Model: Subaru EJ series (Flat-Four), Phase 2, Model
EJ204 (Naturally Aspirated).
Engine Type: Horizontally-opposed four-cylinder (flat-four, boxer),
longitudinally front-mounted, four-stroke cycle, water-cooled, naturally
aspirated gasoline engine.
Fuel Management: Sequential Multi-Point Fuel Injection (MPFI).
Valve Timing: Subaru Active Valve Control System (AVCS) on intake
camshafts (variable valve timing). Aspiration: Naturally aspirated.
Bore: 92.0 mm / 3.622 inches. Stroke: 75.0 mm / 2.953 inches.
Displacement: 1,994 cc / 121.7 cubic inches.
Compression Ratio: 10.0 : 1 or 10.7 : 1, depending on specific
application and market.
Firing Order: 1-3-2-4. (Cylinder numbering: Left bank 1-2; Right bank
3-4. Front cylinders are 1 and 3).
Rotation Direction (from front/crank pulley): Clockwise.
Maximum Power Output (JIS Net): 108-118 kW (147-160 Hp) at 6,000-6,400
rpm.
Maximum Torque: 186-196 Nm (137-145 lb-ft) at 3,200-4,400 rpm. Redline:
6,500-6,800 rpm.
Fuel Requirement: Regular unleaded gasoline (91 RON / 87 AKI) is
typically sufficient, though higher octane may yield slight efficiency
benefits.
Emissions Compliance: Meets Japanese and Euro 3/4 standards of its era.
Construction: Cast aluminum alloy with an open-deck design. This is a
key distinction from turbocharged EJ20 engines, which use semi-closed or
closed decks. The open-deck design is lighter and provides adequate
strength for the lower cylinder pressures of naturally aspirated
operation.
Cylinder Bores: Cast-in iron liners (dry liners) pressed into the
aluminum block.
Crankshaft: Nodular cast iron, supported by five main bearings.
Main Bearings: Steel-backed, aluminum alloy shell bearings.
Pistons: Cast aluminum alloy with a specific crown shape for the
compression ratio. Does not feature oil cooling squirters (present in
turbo engines).
Connecting Rods: Powdered metal forged steel.
Oil Pan: Stamped steel oil pan. Some applications may have a cast
aluminum pan.
Balance: The horizontally-opposed layout inherently cancels primary
vibrations, providing smooth operation.
Construction: aluminum alloy, one per bank. Phase 2 design with
integrated exhaust manifolds (the exhaust ports exit directly into a
manifold casting that is part of the head).
Valve Arrangement: Dual Overhead Camshafts (DOHC) per bank (four total).
Intake camshafts are equipped with Subaru's Active Valve Control System
(AVCS), a hydraulically actuated, electronically controlled variable
valve timing system.
Valvetrain: Camshafts act directly on buckets with shims for valve
clearance adjustment (shim-over-bucket design). This is a reliable but
maintenance-intensive design.
Combustion Chamber: Pent-roof design with centrally located spark plug.
Valve Seat Angle: 45 deg. Valve Diameter: Intake: 36.0 mm (1.417
inches). Exhaust: 31.0 mm (1.220 inches). Valve Springs: Single coil
springs.
Valve Clearance (Cold): Adjusted by replacing shims located on top of
the bucket followers. Clearance: Intake: 0.20 +/- 0.02 mm (0.0079 +/-
0.0008 in). Exhaust: 0.25 +/- 0.02 mm (0.0098 +/- 0.0008 in). Clearance
check/adjustment requires camshaft removal.
Camshaft Drive: Single toothed rubber timing belt driving all four
camshafts, the water pump, and the oil pump. Uses an automatic hydraulic
tensioner and idler pulleys.
Injection System: Sequential Multi-Point Fuel Injection (MPFI). Uses
side-feed fuel injectors on most Phase 2 engines.
Engine Control Unit (ECU): Subaru-specific digital ECU that controls
fuel, ignition, and the AVCS system. Fuel Injectors: Side-feed design,
electromagnetic. Flow rate is appropriate for naturally aspirated
application. Fuel Pressure Regulator: Vacuum-referenced, mounted on the
fuel rail.
Throttle Body: Single-bore, cable-operated (drive-by-wire on some later
applications).
Intake Manifold: Composite plastic design, optimized for airflow and
weight savings.
Air Intake: Utilizes a Mass Air Flow (MAF) sensor for load calculation.
Type: Full-pressure, force-fed wet-sump system.
Oil Pump: Trochoid-type (internal gear), driven by the crankshaft via a
hexagon key. Standard volume (10mm) pump. Oil Filter: Standard screw-on
canister type, mounted vertically at the front of the engine.
Oil Cooler: Not equipped on EJ204 engines.
AVCS Solenoids and Oil Control Valves: The variable valve timing system
uses dedicated oil control solenoids fed from the main oil gallery.
Clean oil is critical for AVCS operation.
Oil Capacity (including filter): 4.2 liters (4.4 US quarts / 3.7
Imperial quarts).
Recommended Oil Grade: API SL/SM or later. Viscosity: SAE 5W-30 or
10W-30, conventional or synthetic. Using the correct viscosity is
important for proper AVCS function.
Operating Oil Pressure: At normal operating temperature: 294-441 kPa
(3.0-4.5 kgf/cm2 / 43-64 psi) at 2,000 rpm. Minimum idle pressure: 98
kPa (1.0 kgf/cm2 / 14.5 psi).
Type: Pressurized, forced circulation system.
Water Pump: Centrifugal impeller type, driven by the timing belt.
Thermostat: Wax pellet type. Opening temperature is 76°C (169°F) or 82°C
(180°F).
Radiator: aluminum core radiator.
Coolant Capacity (engine + radiator, approx.): 6.5 liters (6.9 US quarts
/ 5.7 Imperial quarts).
Coolant Recommendation: Ethylene-glycol based, phosphate-free "Subaru
Super Coolant" or equivalent. A 50/50 mix with demineralized water.
Electrical System: 12-volt DC, negative ground.
Ignition System: Coil-on-plug (COP) direct ignition system. Each
cylinder has its own ignition coil mounted directly on the valve cover
over the spark plug, eliminating spark plug wires.
Spark Plugs: Iridium or platinum long-life plugs. Gap: 0.7-0.8 mm
(0.028-0.031 inches). Common plug: NGK IFR6A11 or equivalent.
Emission Controls: Includes Exhaust Gas Recirculation (EGR), Positive
Crankcase Ventilation (PCV), a three-way catalytic converter, and
evaporative emissions (EVAP) system.
On-Board Diagnostics: OBD-II compliant in most markets.
Length (from front of pulley to rear of block): 600 mm (23.6 inches).
Width (over cylinder heads): 750 mm (29.5 inches).
Height (from bottom of sump to top of intake manifold): 600 mm (23.6
inches).
Dry Weight (engine only, complete with intake/exhaust): 130-140 kg
(287-309 lbs).
Engine Oil and Filter Change Interval: Every 7,500-10,000 km
(4,700-6,200 miles) or 6-12 months. Use of quality oil is critical for
AVCS health. Spark Plugs: Replace with specified iridium plugs every
100,000 km (62,000 miles) or as recommended. Timing Belt and Components:
Replace timing belt, hydraulic tensioner, and all idler pulleys every
100,000 km (62,000 miles) or 5-7 years. This is the single most
important maintenance item. Valve Clearance Adjustment: Check and adjust
(via shim replacement) every 100,000 km (62,000 miles). Labor-intensive
but essential for optimal performance and to prevent valve train noise.
Accessory Drive Belt (Serpentine): Inspect and adjust tension regularly.
Replace at signs of cracking, typically every 80,000-100,000 km. Coolant
Replacement: Every 48 months or 100,000 km (62,000 miles), whichever
comes first. Fuel Filter: Replace every 60,000-80,000 km (37,000-50,000
miles). Air Filter: Replace every 30,000-40,000 km (18,600-24,850
miles). PCV Valve: Replace every 60,000 km (37,000 miles) to ensure
proper crankcase ventilation.
Cylinder Head Bolts (Phase 2, M11): Torque-to-Yield (TTY). Must use new
bolts. Procedure: Step 1: Tighten all bolts in sequence to 25 Nm (18
lb-ft). Step 2: Tighten all bolts an additional 90 deg (1/4 turn). Step
3: Loosen all bolts completely. Step 4: Repeat Step 1 (25 Nm). Step 5:
Tighten all bolts an additional 90 deg (1/4 turn) again. Follow exact
factory sequence for each head.
Main Bearing Cap Bolts: 54-59 Nm (40-44 lb-ft).
Connecting Rod Cap Bolts: 49-54 Nm (36-40 lb-ft). Not typically
angle-torque on NA engines.
Flywheel to Crankshaft Bolts: 60-70 Nm (44-52 lb-ft) + 30-degree turn.
Crankshaft Pulley Bolt: 177-186 Nm (131-137 lb-ft).
Camshaft Sprocket Bolts (AVCS): 78-88 Nm (58-65 lb-ft).
Spark Plugs: 18-22 Nm (13-16 lb-ft).
Oil Pan Bolts: 8-12 Nm (6-9 lb-ft).
Valve Cover Bolts: 8-10 Nm (6-7 lb-ft).
Intake Manifold Bolts/Nuts: 18-22 Nm (13-16 lb-ft).
Exhaust Manifold (Integrated Head) Nuts: 30-35 Nm (22-26 lb-ft).
Timing Belt Tensioner Bolt: 39-49 Nm (29-36 lb-ft).
The Subaru EJ204 engine was used in a range of Subaru models for the
Japanese, European, and other international markets from 1998 to 2005:
Subaru Legacy (BE/BH, 1998-2003): Used in various trim levels such as
the Lancaster, RX, and other non-turbo models. Subaru Impreza (GG/GD,
2000-2005): Available in the "Impreza GX" and other naturally aspirated
trim levels outside North America. Subaru Forester (SF/SG, 1998-2005):
Used in base and mid-level naturally aspirated Foresters in many
markets. Subaru Outback (BE/BH, 1998-2003): The non-turbo Outback in
many markets used this engine.
The EJ204 was not sold in the North American market. North America
received the similar but distinct EJ251 (SOHC) and EJ205 (DOHC turbo)
engines. The EJ204 is a JDM/International DOHC AVCS engine, making it a
desirable swap candidate for enthusiasts in other regions due to its
advanced head design and reliability. Its production run was concurrent
with the Phase 2 turbo EJ205 and the older Phase 1 engines.
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